This is probably going to sound dumb, but here goes anyway....

A friend, living outside Brewster, Wash., in Okanogan Co. has heard a
strange sound around 10:00 p.m. It sounds like a person whistling for his
dog -- two notes, slurred together. Very loud. Moves from spot to spot
quite quickly. He lives "out in the country" with only one neighbor on one
side of him. Flycatcher was suggested; but at night? loud??? Any help
would be appreciated. Meredtih Spencer